


Prank or be Pranked

by thejinichan



Category: Undertale (Video Game)
Genre: Comedy, F/M, Feels, Flirty Sans, Fluff and Angst, Fluff and Humor, Pacifist Route, Post Pacifist Route, Prank War, Pranks and Practical Jokes, Reader Is Not Frisk, Reader-Insert, Sans Being Sans, Sans Makes Puns, Slow Burn, Spoilers - Undertale Pacifist Route, Twisted and Fluffy Feelings, awkward moments, embarressment, eventual relationships?, pranking skeletons, reader is female, reader is uptight, sans and reader - Freeform
Language: English
Status: In-Progress
Published: 2016-06-13
Updated: 2016-09-29
Packaged: 2018-07-14 20:11:33
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 6,922
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7188371
Author URL: https://archiveofourown.org/users/thejinichan/pseuds/thejinichan
Summary: <blockquote class="userstuff">
              <p>Monsters have been on the surface a few years now, and you have just landed a job at Golden Hills, a school opened by Toriel for Monster and Humans alike. You are super excited to start the year and teach your class, but someone is playing pranks on you. Just who could the prankster be? Certainly not a certain skeleton that's for sure. Let the war begin.</p>
            </blockquote>





	1. The jokes are on YOU

**Author's Note:**

> This is my second Undertale fic!
> 
> Originally It was going to be my first, but it ended up being put on the back burner for some time. Anyways be prepared for a lot of hilarity! and Jokes! and Puns! This fic will have Sans at his best! And Reader is a bit of a hardball...and has a hard time with jokes...well, she is going to learn the hard way!!!
> 
> I have a tumblr...come follow me if ya like!
> 
> www.thejinichan.tumblr.com

You should have known you were in for some trouble the second you sat down on your chair, on the first day of school. The noise ripped right through the silence of the class full of grade 2 students you had just finally managed to settle. The whoopie cushion flapped it’s ridiculous song under your rear, while the class burst into an uproar of laughter.Mortified, and Red in the face, you did your best to calm the children down, but your efforts were thwarted.  

Nothing to freak out over, just a little practical joke right? So you smoothed out the wrinkles in your skirt and stood up, tossing the offending whoopie cushion in the trash bin. You could let it go..just a little practical joke, from a student in the room. Just a kid, being a kid. You regained your composure and began the lessons you had scheduled for the day. It wasn’t going to effect your day. 

This wasn’t your first teaching job, nor your first time dealing with a class clown, but it was your first time, teaching and working alongside monsters. Golden Hills, named for the fields of golden flowers that surrounded the school, had been open for a few years already, since the barrier had broken. It was the first school of it’s kind, being open to both monster and human children alike. You were more than eager to apply for the job when you saw it posted, since it meant moving back into your hometown and out of the city. You were delighted after receiving a call to be interviewed, and over the moon happy when you got the job.  

But you should have known. 

On your lunch break that day, someone had replaced your lunch with packets of ketchup. You sighed, wow, there was some kid in your class who was hell bent on pranking you good. You pondered for a moment how a student could have gotten into the lunchroom, and glanced around at the staff in the lunchroom, searching for a guilty face. 

Undyne, the gym instructor could no longer be silent and she doubled over in laughter. She laughed until her blue face was as red as her hair, slamming a fist into the table. It wasn’t that funny. 

You emptied out the stash of ketchup packets onto the table, and crossed your arms. Was it Undyne? She only shook her head at you in denial and snorted.  

Luckily you had packed extra snacks, always be prepared you told yourself. Rummaging around in your purse, you produced an apple. Your stomach stopped growling, as you munched the fruit hungrily. 

You took no notice, to the janitor cart parked outside the lunch room and the Skeleton leaned up lazily against it. Sans was it? You had met him and his brother a week ago at a picnic held at the beginning of each school year. You were totally fascinated by the two, even now. Aside from first introductions, and the promise of spaghetti from Papyrus, you hadn’t talked to either of them that much.   

Sans caught you staring at him as you were in mid chew, and you froze. He just stood there grinning and winked at you. How does a skeleton even do that? You turned away, blushing, over the fact you were caught staring. You couldn’t help it, his facial expressions were just something to behold. He continued his to make his way down the hall, until you could no longer see him from the door. 

After lunch, you felt more relaxed being back with your students, and eased yourself into the afternoon activities. You loved teaching, and ever since you were a little girl, it was all you ever dreamed of. You always had your nose stuck in a book. Your mother used to chide you for not being more outgoing, but you always reminded her that there was more to life then socializing. There were young minds that needed to be molded, and it was your job to ensure they were taught. 

With the end of the day announcements from MIss Toriel, and the steady ringing of the bell, To your relief, it appeared you would be able to leave without being the victim to anymore immature practical jokes. You smiled warmly and thanked the class for a great first day, and bid them farewell. They all eagerly filed out into the hallway, grabbing their bags from their lockers, lost in the chatter of and excitement from the first day. Your smile turned into a grimace, when you overheard two boys laughing over the whoopie cushion from the morning. Boys will be boys, you told yourself, laughing it off silently. Somebody had their fun, and now that it was over, you could concentrate on more important things, like the next days itinerary. 

But you should have known not to let your guard down because when you opened up the top drawer of your desk to retrieve your laptop, a spider sprang out, and landed on your lap. You were not prepared for this outcome, and you screamed as it bounced around in your lap. You shot up from your seat, flailing your arms in the air. Somehow, the offending creature was now stuck to your skirt, and you hastily swatted at it. That’s when you realized it was only a fake. 

Breathe. 

You inhaled a deep breath and slunk back into your chair, hands on the table. Someone was messing with you badly. Someone that was trying to push your buttons.  You didn’t have time for this.  

And that’s when you heard the chuckle. 

Standing over in the doorway, hands stuffed in his pockets was Sans. He merely smirked at you, with a brow raised. 

“Wow! You got some pretty sweet dance moves there, teach.” He grinned 

You nervously smiled, and could feel the hotness begin to bloom in your face. 

“Y-you saw that??” You stammered. 

“Sure did Teach, you might wanna consider trying out for the talent show next month” He teased. “I’m sure you’d get first place, well..you’d have my vote at least.” 

You half smiled at his attempt to joke. “ Haha very funny...and I have a name you know..” 

“Teach suits you so much better though, I think I’ll stick to that.” 

You nodded, not a huge fan of nicknames, but aside from the pranks, it was nothing to get upset over. Sans seemed to refer to most of the people he knew as chum, pal, or kid. At least this was what you heard in passing. He seemed to be a quiet guy, and being a janitor suited his nature. You even caught him sleeping once, something you would NEVER do.  

You sighed and opened up your laptop. “You wouldn’t believe the day I’ve had” One of my students has it in for me I think. First the whoopie cushion, then the ketchup packets at lunch! Where does a kid even get that many packets of ketchup?” And now the fake spider, when you caught me...dancing.” You were furiously typing away at a schedule for the next day. 

“Oh ya?” He muttered. “Sounds like someone is getting you real good.” 

“Real good. But I’ll find out, it’s always easy to pinpoint the class clown.” 

“Is that so? So tell me then Teach..what would you do if the offending class clown happened to be standing right before ya?” 

You shut the laptop and locked eyes with the skeleton. “I would ask them to stop? Once they see the error of their ways, they are sure to stop. Practical jokes are only a disruption to the days lessons.” 

Sans shrugged, “I gotta tell you though teach, it’s not always that easy though.” 

You raised an eyebrow in response. “Wait, what? What do you mean by that?” 

He laughed again. Sans had a nice laugh, it was low, and not too loud. It was the kind of laugh you could get used too. 

He shuffled over to the desk and gripped the edges of it with his bony hands. He was almost right in your face. You instinctively backed up, as it was too close for comfort. 

“If you ask said prankster to stop, it may have the opposite result. Trust me.” 

 “Has this happened to you before?” You questioned him. 

“Nope, not really.” His eyes squinted, as his smile cracked into an even huger grin. He was struggling to keep it down. 

He closed his eyes, and stepped back, returning his hands to his pockets.  

“Well teach, gotta run, got a ton of work to do. He muttered. 

“A skeleton." 

You groaned. 

“Come on, it wasn’t that bad...your smiling.” 

He saluted you from the doorway. 

“Welp, we’ll have to ketchup later ok? See ya” 

He hummed while rolling the cart down the hallway, and you rolled your eyes at that last pun. Ketchup later...ohhh boy, something told you he had a million of these lines.  

You should have known. 

And that’s when it hit you.  

The realization washed over you suddenly. You sprang from your seat, and ran down the hallway, almost slipping in the process, and caught up with Sans. 

Panting, you shakily pointed a finger at him. “It,- it was you, wasn’t it? 

 "A prankster never reveals himself.”  

 “It was you I know it!” You huffed. 

  

“Lemme give you some advice ok Teach?” Sans spoke very calmly on the matter. 

  

“In this school its either prank, or be pranked.” 

 


	2. Thoughts of Revenge

**Summary for the Chapter:**

> Time to get even with the skelly! 
> 
> *MEGALOVANIA INTENSIFIES*

So Papyrus was totally suited to be the school chef. He was on top of his game working in the school cafeteria, donned in a chef’s hat and frilly blue apron. He always had a huge smile plastered on his face as he gleefully tossed food onto the trays of the students. The kids loved him too. 

  

“Ah! So I see you could no longer deny the anticipation trying my artisan pasta! He beamed while waving a spatula in the air. “And you are in luck since today is Spaghetti Tuesdays Nyeh!” 

  

You eagerly held up your tray as he spooned a heaping portion onto your tray. “No I couldn’t! But to be honest, I didn’t want to risk getting ketchup a second time...thought I’d try my luck here.” 

  

Papyrus gave you a curious look and pondered over what you said for a moment. “Hmmm ketchup you say? There is only one skeleton I know who enjoys that  particular condiment to that scale.” 

  

“If you see your brother tell him I’ll pass today.” You chuckled. “Thanks for the pasta Papyrus! It looks amazing!” 

  

“You are most welcome human! Be sure to stop by Master Chef Papyrus’s kitchen for more meals to tantalize your tastebuds!” 

  

You scanned the cafeteria for a table, and noticed Alphys amongst the crowd, all the way in the back. You wove your way through the mass of schoolchildren, holding your tray above your head. You plunked down next to her., She was happily slurping up noodles from her ramen cup. 

  

“H-hey” Alphys timidly stammered, slurping up the last noodle from her chopsticks. “No ketchup today?” She broke into a fit of giggles. 

  

“No not today” You rolled your eyes. “I can’t believe him! Where does he get off pranking people like that?”  

  

“D-don’t take it so hard.” She replied, waving a clawed hand. “Sans does that to all the noobs.” 

  

“Noob?” 

  

“Y-yeah, you know..since your the newest member of the faculty. We’ve all been through it...He’s even pranked me.” 

  

Oh ya? And what did he do to you..? 

  

Alpyhs thought for a moment as the memory came flooding back to her. 

  

“S-so I am the science teacher right? “S-so I’m about to start a lesson with my students..and I had, set up a projector...for my presentation...on rocks and minerals and he replaced it w-with Mew Mew Kissy Cutie Pictures. T-the class was all laughing, I was s-super embarrassed, b-but w-we ended up talking about our favorite anime’s instead...s-so I guess it wasn’t all that bad?” 

  

Alphys pushed up her glasses and smiled at you..”B-but don’t worry! He usually stops after the f-first day, s-so you can relax?” 

  

“Hmmm I guess” You pondered, remembering your conversation with Sans the day before.  

  

“T-thats the spirit!”  

  

You should have known though. 

  

That afternoon when you walked back into your classroom, there was an airhorn taped to  the wall directly behind the door knob. So of course, when you swung the door open, the shrieking wail made you jump six feet into the air screaming. 

  

Laughter. Endless Laughter. You were on the ground now, struggling to get up, ears still ringing from the outburst. The laughter stung your still sensitive ears. 

  

One of your students, Frisk, Toriel's adoptive child came over to you. They were giggling a bit over what had transpired. But even so, they appeared to feel bad. They offered a hand to help you up and gratefully, you accepted.  

  

Settle the class, yet again. Did that skeleton have any idea how hard it was to calm down a roomful of twenty-five 7 and 8 yr olds? You’d like to see him try. By now, you were sure that all your students though you were a joke, just something to laugh at. But you still had a job to do, no matter how flustered you felt. 

  

But you weren’t going to let him get away with it. Not this time. The wheels in your head were turning and twisting with nothing but thoughts of revenge. 

You were gonna get him back, really good. 

  

The next day, you arrived a few hours early, just as the sun was peeking over the side of Mount Ebott, standing tall in the hazy morning light. You shot Asgore a quick wave, as he was trimming a hedge with a large pair of shears. Aside from him, no one would show up at this ungodly hour. 

  

But you had a mission, and had to see it through. 

  

The sound of your footsteps echoed loudly in the empty hallways. You passed Toriel’s office and the door was wide open. You slowed your pace, to check to see if she was around. After all...you didn’t want to anyone to know what you were up too. 

  

“Howdy there!” 

  

It was just flowey, the flower, Toriel carried him everywhere, and right now he was perched atop the large mahogany desk in a light blue ceramic pot. He cocked his head to the side, giving an eerie smile. 

  

“And what might you be up too at this hour? Your not getting into any trouble are ya?” 

  

You shot Flowey the most innocent look you could give. “N-no! Just came early to get a head start on things.” 

  

“Suuure you did!” The Flower sneered at you. God, he creeped you out, sitting there, looking all cute. It really sent shivers down your spine, since it felt like he might have an inkling as to what you were up too. 

  

“W-well tell Toriel I said good morning! Er... Got to run bye!” You stammered while giving a quick wave. You heard flowey mumble something but didn’t stick around to hear any more of his banter. 

  

You reached the staff room and opened up the fridge. 

  

Bingo. 

  

On the shelf, there was a single bottle of ketchup in a plain red bottle. I wonder who that could belong too? You smirked, and reached down deep into the bottom of your purse. Could you really go through with this? It was so unlike anything you had ever done before. 

But if a war was what Sans wanted...it was a war he was going to get. 

  

Your smirked as you pulled the item out of your bag. It was a bottle of Hot Sauce, the biggest, hottest stuff you could find. 

  

Butterflies were nervously flapping around in your stomach, and you set the ketchup and hot sauce down on the counter. You were nervous, but eager to exact your revenge on the skeleton. 

  

Hands shaking, you twisted the lid off the ketchup bottle, and began to dump its contents into the sink. You turned the tap on to wash the remaining evidence away. You grabbed the hot sauce, tipping it upside down, filling the empty bottle until it was almost bursting at the rim. When you twisted the lid back on, some sauce oozed out from the side and onto your hand. Ouch. You could feel the heat even on your skin. 

  

You felt so evil, thinking of how shocked Sans was going to be when he took a swig. A sudden pang of guilt stabbed you, but you ignored it and put the bottle back into the fridge, shutting the door lightly. 

  

You let out a sigh of relief. 

  

Mission Accomplished. 

  

Now all you had to do was wait. 

  

That afternoon at lunch...you sat impatiently with the other teachers. The bottle was still in the fridge. You were going to wait, and relish in the moment of your revenge. 

  

A few minutes later, Sans came strolling in, and gave a lazy wave, making yet another skeleton pun. He winked at you, and you shot him a mischievous smile. 

  

He grabbed the condiment from the fridge, and leaned up against the counter on his elbow for support. He had one hand in the pocket of his brown cargo shorts. Sans raised the bottle to his mouth and he gave it a squeeze, chugging it. 

  

You were gripping the edges of your chair, hard, waiting. This was it. 

  

Sans eyes opened wide, pupils gone, and made a muffled choking noise, mid-chug. His entire skull took on the hue of the hot sauce. Fiery Red, He coughed, and dropped the bottle. He scrambled over to the sink, shaking and shoved his head under the tap. He turned the cold water on full blast, it came roaring out. 

  

Sans brought his mouth to the tap, gulping as much water as he could take in. It began pouring out of his eyes sockets and nose. 

  

A rush of quiet filled the room, spare for a few gasps here and there. Now, seeing Sans coughing and sputtering under the tap, you felt a little ashamed Well this was way more embarrassing than anything he did to you. Pangs of guilt stabbed your stomach, and you found yourself regretting the entire thing. 

  

SMACK!!! 

  

FUHUHUHUHU!!!!! 

  

Undyne had swatted your back, and was cackling. You winced. 

  

“Man on man!! You got him REAL good didn’t you?” “You better watch out for this one Sans!!” 

  

“W-wait you squeaked. “H-how do you know it was me? It could have been anyone..’  

  

Sans yanked his hood over his hand and rubbed it on his face to dry off. Once he regained his composure, he locked his eyes on you, his sockets black bottomless pits. You shivered, as he stared at you. He just stood there, smiling...and you couldn’t read his expression. It was really intimidating, and your heart began to pound. 

  

You were about to get up, when he instantly popped in front of you. Wait. How did he do that? You backed up slowly, into the wall..and he trapped you there, with both his arms firmly planted on either side of you. 

  

His pupils came back, shining like little pinpricks and he slyly smiled at you. Sans was still sweating from the heat of the hot sauce. 

  

“Not bad Teach” He spoke quietly, and you could feel his breath on your cheeks.“Tibia honest..I was expecting something...but not to that degree..man...you really know how to turn up the heat dontcha?” 

  

A small squeak was all you could manage..and you shrank down. 

  

“I-umm...I...” 

  

He grabbed your chin and came right down into your face. “It’s on.” 

And he vanished, in an instant, just like that. 

  

You crumpled to the floor, mortified. Hushed whispers filled the room. You slowly stood up and wiped the dust from the floor off your jeans. 

  

“You better watch your back now.” Undyne threw an arm around you. “You messed with the wrong skeleton.” 

  

You groaned...did you, just make the situation worse? Just...what, were you going to do now? All you wanted to do was get even. 

  

But now you found yourself in the midst of a prank war, with the school’s best prankster. 

  

**Notes for the Chapter:**

> I am having so much fun with this! OMG!!!
> 
> Shoutout to my friend Syrei from Tumblr for the prank on Alphys.
> 
> I'm thinking down the road eventually...I may take prompts on my tumblr for pranks!! If you can think of a good one, send it over to wwww.thejinichan.tumblr.com 
> 
> Poor poor Reader...she's in for it now...~cackles evily~


	3. Finders Keepers

**Summary for the Chapter:**

> Things are now going missing in your classroom. What's a teacher to do?

  

Was there a phantom in the classroom? It was beginning to feel that way.   

It started with little things, that normally you would’ve never noticed. You turned your back for a moment, to grab a piece of chalk, to write an equation on the board. but you were stopped cold in your tracks. The whole box had mysteriously disappeared. Dumbfounded you looked around, kneeling down to check under the table. 

Nothing.  

You didn’t realize that you had run out, but it was nothing that a trip to the supply room couldn’t fix. 

But soon, you found yourself running out of all sorts of things. Paperclips, pencils, the stapler. More trips to the supply room. It was getting a little weird, since you were absolutely sure that most of the items had only been there a moment ago. You had always prided your organization skills to be top notch.  

That was until, you were in the midst of starting a lesson one day, and the textbook that had just been resting on the edge of your desk vanished, instantly. Distracted by the muffled snickers of your students, you whipped your head around to shush them with a finger. They did their best to contain their giggles behind their tiny hands. Feeling satisfied in having silenced the ruckus, you reached over to retrieve the text book.  

And just like that, it was gone.  

You didn’t find this funny, not in the least, but the children sure did. 

And Frisk just sat their, all innocently...twiddling their thumbs, pretending to not have a clue as to what might be going on. 

By now, you should have known and you cursed the culprit silently. 

During recess, you trumped relentlessly around the school, searching for the skeleton.  Where was he? You couldn’t seem to find him. You asked a few co-workers, though they also didn’t seem to know Sans’ whereabouts.  How convenient was it that he was nowhere to be found? By now, you knew he would be back for more. 

 

That afternoon, while in the middle of a math lesson, Sans instantly appeared in front of you. Startled, you froze and dropped the pointer stick in your hand. It bounced off the tiled floor with a thwack. 

“Hey kids!” He removed a bony hand from his pocket to wave. He shot you a small smile. 

“Sup Teach!” 

You could already begin to feel your face redden. It was the middle of the day, in the middle of an introduction on multiplication. Didn’t he know it was rude to interrupt? Did he enjoy pushing your buttons like this? 

“You do know, there’s a door right? You could always knock if you wanted to join in on the lesson.” 

Sans shrugged, but bent down to pick up the pointer stick you had dropped. 

“No worries, teach, I already know how to multiply, heh, I only dropped in, to see if there was any more stuff laying around.”  Sans waved the pointer stick slowly in front of your face. “Whaddya think kiddos? Should the teach be throwing her stuff around so carelessly?” 

They chorused in a simultaneous “NOOOOOOOOOOOOO” 

He slammed the pointer into his palm, and smirked mischievously. “If you want this back teach..and your other things...drop by the lost and found after the bell rings.” 

Sans saluted the kids, before blipping away, instantly, yet again. 

One of your students raised a hand, before speaking and their voice was tinged with excitement.. “Does this mean math class is over?” 

How were you supposed to compete against a magical monster that knew your every move? The more you thought about it, the more bothered you became. It just wasn’t fair. 

  

At the end of the day, you stopped by the lost and found. It was one of those half door deals...and the top half was swung open. You peered inside to see Sans snoring, back against the wall and propped up on a stool. 

“Sans?” 

Snore.Snore. 

“SANS? 

More snoring. 

You sighed...tapping your foot impatiently. 

“SAAAAAAAANS!!!” 

His eyes finally blinked open slowly. He sat up a bit to stretch, casually, like he didn’t even notice the fact you just hollered in his face. 

“Ya know, you sound ALOT like my brother when you yell.” He joked.  

“How else was I supposed to wake you? You sleep like the dead.” 

Heh..hehheh, good one teach” Sans chuckled. You told a pun, not even realizing you had. 

“Oh my god! You stammered. “ I didn’t mean...for it to come out..like that...”  

The skeleton lazily waved a hand and chuckled. “No offence taken..it’s all good, and besides, it's nice to know you have a humerus side.” 

 Your frown rose into a half smile. Did he find you funny? You had never considered yourself to be a funny person. Yet here you stood..making jokes with someone and not even noticing. You were treading on unknown territory. It was new, and it made you feel nervous. 

“So, ummm anyways” You muttered, switching the subject. “I would really like my things back now..” 

Sans rested his skull on his hands, over the top of the half door. “You sure did leave a lot of stuff just laying about....it kinda looked like my room…we have that in common at least right” 

You shot him an annoyed glance. “None of that stuff was just laying around...it was on my desk! In my classroom!” 

Sans closed his eyes and sighed. “Well finders keepers teach.” 

You crossed your arms. “Well why bring it to the lost and found then?” 

Sans shrugged and sat up “Alrighty Teach...you win, you can have your things back.” He started rummaging through the various shelves, and brought out all the things he had procured. He set the massive heap of items he had collected in front of him. Some paperclips, and erasers escaped the pile, rolling onto the floor. 

You stared at the pile in disbelief. He really had taken more things then you realized. He was good at this. Too good, and you didn’t want to admit it.  You reached over to take your things, feeling thankful you would finally have your supplies back. After a few days of constantly misplacing things, it was a huge relief. 

but Sans abruptly stopped you, shielding the pile with a billowy blue sleeve. 

“You can have your stuff...but it’s gonna cost you.” 

“Saaans come on now!!!” You rolled your eyes in annoyance. 

Yes Papyrus?” 

“For the love of GOD” You stammered, “Can’t you just let it go already? I, just.. want my stuff back..please....and if this is about the hot sauce...if I went overboard, I’m sorry.” 

Sans merely grinned at you. He never stopped grinning. His expressions never changed. Unlike the kids in your class, you could never read Sans. It made you feel uneasy, not knowing what he might do or say next. 

Somehow you had to fish your way out of this...by stopping to his level. What could you do? Or say? Puzzled, you thought for a few moments, and spat out the first thing that came to mind. 

“Ummmm I dunno...er...can I start a tab?”  

Sans eyes lit up when you said this. There is was. All you had to do was join in on his little game. You breathed a sigh of relief while he handed you your things. 

You could barely keep hold of everything in your arms now, and the pile was awkwardly blocking your view of the monster. Even after all the games you turned to the side to thank him, hands grasped tightly so nothing would escape. 

He lightly laughed watching you struggle to keep it all together. 

“Need a hand teach?” 

You shook your head. “No…I think, I’m ok…er thanks anyways.” 

The skeleton threw his arms behind his skull and returned to his leaning pose against the wall.  “I’ll expect payment with interest Teach...otherwise if you leave things laying around again….well, I am the janitor after all riiight?” 

“Yeah, yeah” You joked. “I’ll remember that.” Right now you were just happy to have your things back. 

When you returned to your classroom, you made sure to put everything away. You made sure there wasn’t a single thing lying about, right down to the last pen. You let out a contented sigh when you were finished, feeling pretty positive he wouldn't find anything else to swipe. 

  

You stuck around into the early hours of the evening, grading some papers, outside on one of the benches that surrounded the schoolyard. It was a beautiful brisk fall day. The leaves were just starting to change color and there was a slight cool breeze. As it rolled by, some of your papers ended up scattering in the wind. They flew around, dancing through the air around you and clumsily, you tried to gather them back together. By now your hair was blowing into your face, and you cursed yourself for not wearing it up. 

Just then You saw Sans and Papyrus making their way down the schoolyard. Just as the last sheet, floated above your grasp, Papyrus reached it with ease and handed it to you. 

Out of breath from running about, you tucked your windswept locks behind your ears and eagerly accepted the paper back. 

“Thanks Papyrus!”  Your a lifesaver!” 

Papyrus gave you a puzzled expression. “You are most welcome human!” Though...why are you referring to me as one of those colorful candies the children always have…BUT WAIT!!!”

 He slammed a fist into his open palm, still wearing his oven mitts. “ You must think I’m sweet right?” You are most kind for thinking so!!” 

Papyrus picked you up and squeezed you. You had never hugged a monster before. For having such skinny arms, he had a strong hold. Your feet dangled in the air. You blushed as he set you gently back on the ground. 

Aside from them both being skeletons..how could these two be related? They were so different. Papyrus was a sweetheart, always looking out for others...and Sans was just. well he was Sans. 

Sans was scanning the ground and found the pen you had been using to mark your worksheets. He bent over and picked it up, twirling it between his bony fingers. 

“Tsk tsk, I thought you learned your lesson earlier Teach.” He mockingly scolded you.  

You held out your hand and glared at him 

Sans winked. “Finders Keepers remember?” 

Papyrus raised an eyebrow, “Saaaaaans! Quit teasing the poor teacher! She clearly needs the writing instrument to complete her work!! Quit boondoggling and give it back!” 

“She left it on the ground though bro.” 

“She dropped it SANS!” 

Ok, ok, I guess I’ll let it pass this time.” He handed it back to you. “That’s gonna cost you too though.” 

“Guess I’m gonna have to start saving then.” You muttered sarcastically, ending it with a small snicker. It just escaped. You didn’t want him to think you found this funny, because you knew then, he would never stop. 

“Sans pupils grew larger for a moment. You noticed he always did this when you made a joke, no matter how small or indirect it seemed. He looked impressed. 

“That’s the spirit Teach” 

You pondered just how much money he was going to ask you for...and then an idea came to mind. 

You knew just what to pay him back with, and you smirked while thinking so. 

  

  

  

  

 

**Notes for the Chapter:**

> I am so sorry for the wait!  
> O_O It's been a really crazy summer for me..and I was picking at this slowly. I hope you guys enjoyed the end result! I am having a blast with this fic so far!!!  
> Also thank you to Skelewriter for the writing prompt on this chapter. Sans appearing and dissappearing..and stealing things from the classroom.  
> If you have an idea for a prank that the teach or Sans can pull on eachother, drop me a msg at my tumblr,  
> www.thejinichan.tumblr.com


	4. Operation Cleanout

**Summary for the Chapter:**

> Time to settle your tab! Once and for all you hope!

After talking to Sans and Papyrus, and instead of heading back home, you returned to the school, filled with anticipation. Inspiration had just struck, and you had to act on it. 

But first you were going to the master set of keys from the office, which meant running your plans by Toriel first.  

Whatever happened to just doing your job? That was after all, all you wanted in the first place. You considered yourself a sensible person, and there was a roomful of 25 students, that you had to set the proper example for. 

And pulling pranks and jokes constantly, was not the kind of role model you ever expected yourself to be.  

But here you were, doing exactly that. 

Toriel giggled at you, as you explained your plan passionately. It was brilliant. It was foolproof. And you knew it was going to work. Maybe finally, after everything that had happened, Sans might see that you were indeed, a force to be reckoned with. You tried your best not to burst from excitement, from the thought of the skeleton throwing in the towel. 

You were a little shocked, after explaining, that Toriel didn’t seem to mind at all. She unlocked the bottom drawer in her desk, and handed you the keys without hesitation. You eagerly accepted and they landed into your palms with a jingle. 

Dumbfounded, you asked her once more. “Are you sure this is ok?” 

Toriel nodded. “Yes..just return them to the office once you are finished. Honestly, I’m just happy that you two seem to be getting along so well.” It's always wonderful to see members of the faculty hit it off the way you two have my dear.” 

You shifted uncomfortably in your seat. Get along? If what she was saying was true..Sans had a funny way of showing kindness. Maybe once you carried your plans out, and had settled your pranks once and for all, you could focus on becoming more acquainted with the monster. 

A part of you would be lying though if you didn’t find some of the things he did amusing…even if you were irritated sometimes that he interrupted class…or scared the living daylights out of you. 

Doing things like this, was not in the job description. 

You started in the staff room, emptying the fridge, then you purged the mini one in the utility closet. Then it was over to the cafeteria kitchen, and the walk in fridge….with it’s large stainless steel doors. The air inside it made you shiver while you worked, grabbing every single bottle you could find, loading it all into a large crate. 

Right down to the last ketchup packet. 

You left Papyrus a little note, explaining your intentions. You were pretty sure he would understand. 

Sans didn’t know what was coming to him. 

 

The next day when you arrived at school, you found Sans sluggishly dragging a mop across the floor in the hallway.  

“Mornin Teach.” He mumbled, with half lidded eyes. “Howsit goin?” 

“It’s goin..and yourself?” 

He gave the mop a slight shake in response. “Just doing the tango with my dance partner here, she’s pretty cute huh?” 

“Oh yeah, she’s totally hot.” You teased. “If your type happens to be the **washed** out sort.” 

This elicited a small chuckle out of the skeleton. “ What can I say…she’s got a really **bubbly** personality.” 

“Oh my god Sans.” You groaned. “Your terrible!...and I need to get to class…I’ll see you after…ok?” You waved him off quickly as you briskly walked away. 

“If I’m so terrible then why are you laughin Teach?” You heard him say when you timidly shut the door. 

Soon the children in your class began to shuffle into the room, and you were eager to get the day’s lesson’s started. You started the day with show and tell, something you held at least once a week. You loved seeing the enthusiasm etched on the faces of each child, as they talked about some of their most prized possessions. One child brought in a frog, another their rock collection. Frisk brought in some drawings they did about their experiences in the underground, and shared stories on how they had come to free the monsters. It was an exciting tale, and it was easy to see why they were so loved by their classmates. One child brought in a spider, almost as big as the fake one Sans had left on your desk. You felt relieved this one was contained in a jar at least. 

That took up a large part of the morning until recess, and as the students grabbed their coats to play outside, you couldn’t help but wonder if Sans had discovered just what you had done. You were caught in that thought, peering out the large windows at the playground, when you felt a strange presence overwhelm you. 

Suddenly, a set of bony fingers wrapped around your arm and spun you around. 

 You gasped, and Sans glared at you deviously, his large white pupils shining in their black sockets.  

“Ya know, I got to hand it to you teach…stealing every single bottle from the school?, even the lunch packets…heh.” He blinked slowly, his grin never faltering. “That’s the second time you’ve messed with my ketchup now.” 

You did it! This was it…finally you had gotten him, and it took everything in you to keep your composure. You wanted to savor this moment forever. You yanked your forearm out of his grasp and stared at him proudly, feeling very much accomplished in your efforts. 

“I can get it back for you, if you want…” You said coyly. “But it’ll cost you…call my tab even, the pranking even, and I'll give back your precious ketchup.” 

You reached deep into the pocket of your skirt and pulled out a packet, teasingly waving it in his face. “Think about it.” 

“Heh, you’ve forgot something though teach.” Sans reached into his own pocket and pulled out a small slim red bottle. “You failed to raid my own fridge…and I can easily take a shortcut home when I’m thirsty…it’s called majic teach…in case ya forgot.” 

He took a long satisfying swig, and you snatched the bottle from his hands. 

“How am I ever going to win against you?” You spat with frustration. “You are, just, soooooo, impossible!” 

You sighed heavily in defeat, leaning against the wall and shrank down to the floor. Sans sat down beside you, and patted your shoulder lightly. 

“You could try harder maybe…who knows maybe one day you’ll be able to tickle my funny bone.” 

You raised a brow at him. “Why..are you a ticklish skeleton?” 

“Wouldn’t you like to know eh Teach?” 

“Did you REALLY just say that? Oh my god!” You groaned, jerking upright off the ground. You threw the bottle of ketchup into his lap. “I can’t believe I thought that would work…” 

Sans grinned reassuringly at you. “No worries Teach, in the end it was a good try. I can always appreciate a good prank..” 

For a moment, his cheeks, took on a blue hue, but he turned his head really quickly. Was he blushing? No. He couldn’t be could he? So why was he getting flustered all of a sudden?            

Sans extended a hand. “Put er there pal…and I guess we’ll call the tab even.” 

You put your hand out, but stopped midway and hesitated. 

“Heh, don’t worry, no whoopie cushion in the hand…or buzzer..so go on”. He pressed. ‘It’s not gonna shake itself now is it?.” Sans nodded at you in reassurance 

Not sure whether to take his word or not, you nervously took his hand. You lightly squeezed your fingers over his own. While hard, the bones in his hands felt soft and warm. 

Even though you failed in your efforts to get back this time, it felt good to have settled things for the time being at least. For now, you  felt satisfied. 

The bell rang, loudly, signaling the end of recess, and after Sans left, the students began filing back inside, taking their seats. Still chattering amongst themselves, you put your index finger to your lips until you had their attention. 

“Let’s use our inside voices now shall we?’ You said quietly. “And now, if you can all pull out your English books, and turn to page 25, we’ll start at where we left off yesterday.” 

Frisk immediately shot a hand into the air, with a confused look on their face. You nodded at them. “Do you have a question before we begin Frisk?” 

 “ Yes!” They asked you with a puzzled expression. “Why is there dirty socks on the floor?” 

Your face dropped. “What? Where?” Your eyes darted around the classroom in every direction. 

“Behind you!” Another child exclaimed, pointing. 

And there they were, right behind you…a pair of the dirtiest, socks you had ever seen. If they were white once, you certainly couldn’t tell now. They were caked with so much dirt, they had hardened in some spots. Just how long did someone need to wear a pair of socks for them to end up that way? You wrinkled your nose in disgust, and the children only snickered at you, probably wondering why their teacher might leave dirty laundry on the floor. 

On top of the discarded stockings was a yellow post that had some writing hastily scrawled on it in bold black lettering You bent over slightly and squinted to read it, since you didn’t want to touch it. 

STAY DETERMINED TEACH, I’M ONLY GETTING STARTED ;) 

 

**Notes for the Chapter:**

> Silly Teach, you should have known by now.  
> Sans isn't going to stop that easily..It's time to up your game!! :) As always thank you for reading this ficcy! It's a blast writing it so far :3
> 
> If you have any ideas for a crazy prank or situation, drop me a message at my tumblr. www.thejinichan.tumblr.com

**Author's Note:**

> O_O Let the games begin!!
> 
> What do you guys think so far? Would love to hear your thoughts on this little ficcy!


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